The present invention is related to the mounting of a rigid dredge ladder and to the mounting of a holding spud on a dredging barge or dredging platform. It is particularly related to a shock mounting arrangement for a pivotal connection between the barge structure and the ladder structer. It is also particularly directed to a shock mounting arrangement for a holding spud on a barge structure.
Prior dredging apparatus have included pivotally mounted rigid dredge ladders attached to the barge on platform structure. At the end of the rigid dredge ladder opposite the pivotal connection with the barge, a drilling or dredging head was securely attached. The ladder and attached dredging head could be lowered into engagement with the material to be dredged by pivoting about the pivot connection with the barge. With these prior arrangements, the pivotal connection between the dredge ladder and the barge structure provided a rigid continuous structure for holding the drilling or dredging head against the surface to be dredged.
A major disadvantage of this known dredging apparatus arises from the fact that there were no effective means for cushioning shock forces experienced by the drilling or dredging head, such as when it came into contact with rock or other hard surfaces. Consequently, these shock forces were transmitted directly through the rigid ladder to the mounting attachement at the barge or platform. These forces were, in many cases, sufficient to cause extensive damage to the mounting connection between the rigid ladder and the barge structure. Also, the drilling or dredging head and the barge structure itself could be damaged by these relatively unattenuated shock forces.
Since these dredging machines are, of necessity, of such heavy and expensive construction, the repairs likewise are exceedingly expensive. In addition, the money lost due to shut-downs for any repairs are also exceedingly great. For example, dredging machines of the type discussed may have initial cost running in excess of approximately ten million dollars. Therefore, the reduction of repair or dry-dock downtime by even a few days a year would constitute considerable savings.
Another disadvantage of the known dredging apparatus was that the mounting connection between the rigid dredge ladder and the barge or platform was difficult to disassemble and repair. This fact further increased the potential downtime caused by the drilling or dredging shock forces transmitted through the ladder to the barge. In some cases, the failure of a relatively small structural element of the connection between the ladder and the barge would require a complete shut-down of the dredging operation for repair.
Another disadvantage of the known dredging apparatus was that the holding spud for holding the barge or platform in position during a dredging operation was also subjected to shock forces. These shock forces would be transmitted from the holding spud to the barge structure or the spud gate and spud frame holding the spud in position with respect to the barge. These shock forces would be caused basically by high winds and/or swells or waves in the water. The present invention is particularly directed to an improved shock lining or mounting arrangement between the spud and the barge structure such that shock forces are attenuated by allowing a limited radial movement of the spud with respect to the barge structure during extreme swell conditions.